1. Field of the Invention
This invention relates to clamping pins within devices for external fixation of fractured bones, and, more particularly, to an external fixture in which pins are clamped for fixation of multiple fragments of an end portion of a bone.
2. Summary of the Background Art
The fracture of the distal radius is one of the most common human fractures, occurring in as many as 350,000 people per year in the United States alone. The conventional processes both for reducing such a fracture and for maintaining the bones in proper alignment during the subsequent healing process involves applying and maintaining an extension force across the fracture, with ligamental taxis being relied upon to hold the bones in place. The process for treating a fractured distal radius is described in the 1901 edition of Gray's Anatomy in the following manner, “The treatment consists of flexing the forearm, and making a powerful extension from the wrist and elbow, depressing at the same time the radial side of the hand, and retaining the parts in that position by well-padded pistol-shaped splints.”
A common method for the treatment of a fractured distal radius involves the use of standard immobilizing cast techniques, preventing movement of the radiocarpal joint throughout the course of rehabilitation. A problem with this method is that it sometimes results in inadequate internal fixation, which can cause deformity, pain, and prolonged disability.
The process of external pin fixation is often used in the repair of a fractured distal radius. This process initially involves the surgical insertion of skeletal traction pins on both sides of the fracture, with a frame being connected to the pins for immobilizing the bones, and for holding them together until the fracture is mended. Conventional methods for applying external pin fixation for the treatment of a fractured distal radius provide for the immobilization of the radiocarpal joint, so that the hand cannot be flexed.
While this type of fixation often provides an improvement over conventional casting techniques in the management of severe fractures of the distal radius, immobilization of the radiocarpal joint during the treatment period typically results in a long period of stiffness and disability after the external fixation device is removed. Typically, the external fixation device is left in place during the healing process for six to eight weeks. After the fixation device is removed, three to six months are required for the patient to regain motion of his hand.
An example of a fixation device providing adequate fixation during the healing process while allowing flexure in the radiocarpal joint is described in U.S. Pat. No. No. 6,197,027, the disclosure of which is incorporated herein by reference. This fixation device includes a number of pins clamped within pin mounting holes. Each pin extends through a flexible sleeve and through a clamping nut. Each pin-mounting hole includes a pilot hole guiding the pin and an internally threaded portion engaging an externally threaded portion of the clamping nut. As the clamping nut is tightened, the flexible sleeve is longitudinally compressed, so that it expands transversely to clamp itself within the pin-mounting hole and to clamp the pin within itself. The fixation device, which is configured particularly for external fixation of a fractured distal radius, includes a first number of such pins configured for attachment within a shaft portion of the radius and a second number of such pins configured to attachment to one or more fragments of the fractured radius. The fixation device also includes a sliding attachment block supporting a number of pins extending for lateral attachment to such a fragment.
However, in the holes used in the device of U.S. Pat. No. 6,197,027 to mount pins within the first number of pins, what is needed is a somewhat more simple, and therefore cost-effective, method for holding the pins in place. Such a method would preferably eliminate the need for the flexible sleeves to translate longitudinal compression into transverse clamping forces. In the holes used to mount pins within the second number of pins, what is needed is a more simple method, which will preferably clamp all of the pins in use simultaneously. Two or more of these pins may be used to clamp a single bone fragment in two or more places, or several pins may be used to clamp several bone fragments. Furthermore, since the process of setting a distal radius fracture typically includes an application of extension to the distal fragment(s), what is needed is a feature simplifying the application of such extension forces as the fixation device is installed on the fractured radius.
U.S. Pat. No. 5,545,162 describes a bone fixator including a proximal pin mounting block and a distal pin connected by a medial assembly, which connects the pin mounting blocks in a manner which is pivotally adjustable, and which further allows for adjustment of the distance between the pin mounting blocks. However, what is needed is a fixture for facilitating this distance adjustment so that it can be retained and gradually increased, instead of being lost when a clamping screw is loosened to allow movement. Furthermore, the method of U.S. Pat. No. 5,545,162 does not include the installation of pins within the fragments of bone; instead pins from the distal pin mounting block extend into the finger bones, adding a requirement that the extension forces must be directed through the wrist. To provide mobility of the hand and wrist, the fixture is pivoted with a ball joint. What is needed is a fixture rigidly holding pins extending into the bone fragments instead of into the bones of the fingers. Such a fixture would have advantages of holding different configurations of fragments in place, of holding them more rigidly, and of providing greater freedom of wrist movement.
In the lower leg, the tibia includes a long shaft and an extended upper portion which forms a plateau on which the knee pivots. Like the distal radius, this upper portion is prone to fracturing one or more fragments. Such fractures can occur when the lower leg is twisted in a manner not accommodated by the normal movement of the knee joint, as in a football injury, a slip and fall accident, or a motorcycle accident. Conventional treatment of such an injury includes surgically opening the leg adjacent the fracture and fastening various fragments of bone together with bone screws, and with a plate being fastened to the bone to serve as an abutment in holding the fragments in place. In many cases, the plate is later removed in a second surgical procedure after the bone fragments have grown together. What is needed is an apparatus and method to provide for fixation of multiple fragments from the upper tibia without a need to surgically open the area fist for installation of a plate, and then again for the removal of the plate.
U.S. Pat. No. 4,662,365 shows an external fixation device disposed external to the lower leg, including vertical support bar on which pins extending into the front of the tibia are mounted on slidably-adjustable clamping blocks and a horizontal support bar, slidably adjustable on the vertical support bar near its top. A pair of clamped pins, pivotally and slidably adjustable on the horizontal support bar, extend into the expanded upper end of the tibia at opposing angles. What is needed is a fixation device for holding a substantially larger number of pins to extend into the upper portion of the tibia from at different heights and from various angles around the leg, so that a large variety of different types of factures forming multiple bone fragments can be readily treated by fixation. Furthermore, since the process of setting an upper tibia fracture of this kind typically includes an application of extension to the fragment(s), what is needed is a feature simplifying the application of such extension forces as the fixation device is installed on the fractured tibia.
The patent art additionally describes a number of external fixation devices used for treating a fracture of the shaft portion of one of the long bones of the leg by holding pins in place above and below the fracture through an elongated structure extending externally along the leg. For example, U.S. Pat. No. 2,406,987 shows pins or wires extending through the leg and tibia above and below a fracture, with the pins or wires extending between structures of rods extending along opposite sides of the leg. The structures of rods include multiple rods held together by clamping blocks, and the pins are held in place on the rods by clamping blocks. The wires, having a relatively fine diameter, are held in place within U-shaped yokes extending around the leg between the structures of rods.
U.S. Pat. No. 4,662,365 shows an external fixation device disposed external to the lower leg, including vertical support bar on which pins extending into the front of the tibia are mounted on slidably-adjustable clamping blocks and a horizontal support bar, slidably adjustable on the vertical support bar near its top. A pair of clamped pins, pivotally and slidably adjustable on the horizontal support bar, extends into the expanded upper end of the tibia at opposing angles.
U.S. Pat. No. 5,827,284 describes a structure for adjustably clamping a bone screw in place within an external fixation device.
U.S. Pat. No. 3,877,424 describes a method and apparatus for external fixation of bone fractures. The Method comprises inserting at least one pin in each major fragment of bone with a portion of the pins extending above the skin surface, drawing the pins toward one another and applying a bridge to the pins to hold them in place under compression parallel to the bone being repaired. The apparatus is at least two elongated pins adapted to be inserted at one end into the bone on opposite sides of a fracture, bridge means engaging the other ends and compression means acting on the pins generally parallel to the bone.